Radioactivity analysis following the Fukushima Dai-ichi nuclear accident

Model prediction of radioactivity levels in the environment and food around the world's first AP 1000 nuclear power unit

Objectives

Model prediction of radioactivity levels around nuclear facilities is a useful tool for assessing human health risks and environmental impacts. We aim to develop a model for forecasting radioactivity levels in the environment and food around the world's first AP 1000 nuclear power unit.

Methods

In this work, we report a pilot study using time-series radioactivity monitoring data to establish Autoregressive Integrated Moving Average (ARIMA) models for predicting radioactivity levels. The models were screened by Bayesian Information Criterion (BIC), and the model accuracy was evaluated by mean absolute percentage error (MAPE).

Results

The optimal models, ARIMA (0, 0, 0) × (0, 1, 1)4, and ARIMA (4, 0, 1) were used to predict activity concentrations of 90Sr in food and cumulative ambient dose (CAD), respectively. From the first quarter (Q1) to the fourth quarter (Q4) of 2023, the predicted values of 90Sr in food and CAD were 0.067-0.77 Bq/kg, and 0.055-0.133 mSv, respectively. The model prediction results were in good agreement with the observation values, with MAPEs of 21.4 and 22.4%, respectively. From Q1 to Q4 of 2024, the predicted values of 90Sr in food and CAD were 0.067-0.77 Bq/kg and 0.067-0.129 mSv, respectively, which were comparable to values reported elsewhere.

Conclusion

The ARIMA models developed in this study showed good short-term predictability, and can be used for dynamic analysis and prediction of radioactivity levels in environment and food around Sanmen Nuclear Power Plant.

Assessment of radiation exposure and public health before and after the operation of Sanmen nuclear power plant

Introduction

Sanmen nuclear power plant (SNPP) operates the first advanced passive (AP1000) nuclear power unit in China.

Methods

To assess the radiological impacts of SNPP operation on the surrounding environment and the public health, annual effective dose (AED) and excess risk (ER) were estimated based on continuous radioactivity monitoring in drinking water and ambient dose before and after its operation during 2014-2021. In addition, the residents' cancer incidence was further analyzed through authorized health data collection.

Results

The results showed that the gross α and gross β radioactivity in all types of drinking water were ranged from 0.008 to 0.017 Bq/L and 0.032 to 0.112 Bq/L, respectively. The cumulative ambient dose in Sanmen county ranged from 0.254 to 0.460 mSv/y, with an average of 0.354 ± 0.075 mSv/y. There is no statistical difference in drinking water radioactivity and ambient dose before and after the operation of SNPP according to Mann-Whitney U test. The Mann-Kendall test also indicates there is neither increasing nor decreasing trend during the period from 2014 to 2021. The age-dependent annual effective doses due to the ingestion of drinking water or exposure to the outdoor ambient environment are lower than the recommended threshold of 0.1 mSv/y. The incidence of cancer (include leukemia and thyroid cancer) in the population around SNPP is slightly higher than that in other areas, while it is still in a stable state characterized by annual percentage changes.

Discussion

The current comprehensive results show that the operation of SNPP has so far no evident radiological impact on the surrounding environment and public health, but continued monitoring is still needed in the future.

Deposition of Fukushima nuclear power plant accident-derived radiocesium in the soils of Jeju Island, Korea, and evidence for long- and short-lived radionuclides in rainwater

In this study, we investigated the concentrations of Fukushima nuclear power plant accident (FNPPA)-derived radiocesium (¹³⁴Cs, ¹³⁷Cs) deposited in the topsoil of Jeju Island, Korea. We also evaluated the soil inventories of radionuclides and compared the concentrations deposited by rainwater and fallout. We present the first evidence of FNPPA-derived radionuclides directly entering the environment of Jeju Island. In the case of FNPPA-derived ¹³⁴Cs in soil, only a trace amount was identified in the surface layer (1 cm depth), whereas ¹³⁷Cs derived from past atmospheric deposition of nuclear testing were detected along with those derived from the nuclear power plant accident. The total measured radiocesium (¹³⁴Cs + ¹³⁷Cs) indicates that although the value obtained from soils was slightly lower, both values were within the same order of magnitude. Of the FNPPA-derived radiocesium deposited in the soil, the impact from April 2011 was the largest at most sampling sites indicating that the radioactive plume directly covered Jeju Island. Furthermore, a variety of long- and short-lived gamma-emitting radionuclides were detected in the rainwater samples collected on April 7, 2011. Among them, short-lived radionuclides such as ¹⁴⁰La, ^110mAg, ⁹⁵Nb, ¹²⁵Sb, ¹¹³Sn, ¹²⁹Te, ^129mTe, ¹³²Te, ¹³²I, and ¹³⁶Cs, were observed. The findings of this study provide evidence for the direct effects of FNPPA-derived radionuclides in Jeju Island. This is the first location in Korea and the first in the entire East Asian region, excluding Japan that is confirmed to have been directly affected FNPP accident.

An overview of current knowledge concerning the health and environmental consequences of the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident

Since 2011, the scientific community has worked to identify the exact transport and deposition patterns of radionuclides released from the accident at the Fukushima Daiichi Nuclear Power Plant (FDNPP) in Japan. Nevertheless, there still remain many unknowns concerning the health and environmental impacts of these radionuclides. The present paper reviews the current understanding of the FDNPP accident with respect to interactions of the released radionuclides with the environment and impacts on human and non-human biota. Here, we scrutinize existing literature and combine and interpret observations and modeling assessments derived after Fukushima. Finally, we discuss the behavior and applications of radionuclides that might be used as tracers of environmental processes. This review focuses on (137)Cs and (131)I releases derived from Fukushima. Published estimates suggest total release amounts of 12-36.7PBq of (137)Cs and 150-160PBq of (131)I. Maximum estimated human mortality due to the Fukushima nuclear accident is 10,000 (due to all causes) and the maximum estimates for lifetime cancer mortality and morbidity are 1500 and 1800, respectively. Studies of plants and animals in the forests of Fukushima have recorded a range of physiological, developmental, morphological, and behavioral consequences of exposure to radioactivity. Some of the effects observed in the exposed populations include the following: hematological aberrations in Fukushima monkeys; genetic, developmental and morphological aberrations in a butterfly; declines in abundances of birds, butterflies and cicadas; aberrant growth forms in trees; and morphological abnormalities in aphids. These findings are discussed from the perspective of conservation biology.

Fukushima nuclear accident: preliminary assessment of the risks to non-human biota

This study assesses the 'radio-ecological' impacts of Fukushima nuclear accident on non-human biota using the ERICA Tool, which adopts an internationally verified methodology. The paper estimates the impacts of the accident on terrestrial and marine biota based on the environmental data reported in literature for Japan, China, South Korea and the USA. Discernible impacts have been detected in the marine biota around Fukushima Daiichi nuclear power plant. This study confirms that the Fukushima accident had caused heavier damage to marine bionts compared with terrestrial flora and fauna, in Japan.